We propose to examine the problem of differential gene expression during the developmental cycle of Dictyostelium discoideum. Specifically, we plan on examining the structure and expression of developmentally regulated genes in this organism including those encoding the carbohydrate binding protein discoidin I, a lectin known to be involved in species-specific cell-cell adhesion in D. discoideum, and a group of genes whose expression is modulated during development by cAMP. Using recombinant DNA methods, we have isolated two groups of genes whose expression in modulated by cAMP. The first group are genes which are activated early in normal development and which can be induced in suspension culture by cAMP. The second is a population of genes which are expressed late in development and require continued levels of cAMP for expresion. We plan on comparing the biological conditions which affect the activity of these genes and to compare the structure of these genes using molecular techniques. We plan on using a DNA mediated transformation system we are developing to investigate the function of sequences flanking the genes in controlling when during the developmental cycles these genes are expressed and the level of expression of these genes when they are activated. These experiments will be aimed at obtaining insight into the molecular mechanisms by which gene expression is regulated in eukaryotic cells during development.